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3D Scanning System 



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3D Scanning System 

Written By: Andrew Lewis 



TOOLS: 



Band saw (1) 
Drill (1) 
Drill press (1) 
Hacksaw (1) 
Hex wrench (1) 

PC(1) 

Screwdriver (1) 
Soldering iron (1) 

Super glue (1) 

or epoxy. or other contact cement 



PARTS: 






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Aluminum sheet (2) 

Rigid sheet plastic may suffice, but I find 

metal easier to work with and more 

durable 

Spray mount adhesive (1) 
or glue stick 

USB socket (1) 

Copper pipe (4) 

Plastic ball casters (6) 

Bolts (9) 

Bolts (4) 

Photographic gimbal head (1) 

Socket (1) 
inline mounting 

Mono jack socket (6) 
panel mounting 

Hook-up wire (1) 

• Diode (1) 

Bipolar stepper driver/motor combo (1) 
You can also use an Arduino 
microcontroller with a suitable motor 
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3D Scanning System 



shield from makershed.com. 
Plastic worm drive (1) 
Nylon gear (1) 

• Steel shaft (1) 

• Flange ball bearing (1) 

• Project enclosure (1) 

Power supply (1) 

Aluminum sheet (1) 

USB A to A cabled) 

Voltage regulator IC (2) 

Resistor (1) 

/ used these with the LM317to get 4.5V: 
your resistor values will depend on your 
laser's voltage needs. There's a handy 
calculator at reuk.co.uk/LM317-Voltage- 
Calculator.htm. Aim low on the voltage, 
since lasers can be quite fussy about 
maximum voltage. 

Cast phono plugs (2) 

Copper pipe (2) 

Laser line generator (2) 

/ found 5m W. 5V infrared line laser 

modules cheap on eBay. 

Plumbing end caps (2) 

Hot glue (1) 
and/or setscrews 



SUMMARY 

The last couple of years have seen an explosion in home fabrication, with fantastic projects 
like RepRap and Fab@Home really helping to bring the open source community together. 
Unfortunately, 3D scanning — in many ways the flipside of the home fabrication coin — 
seems to have fallen by the wayside. 



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3D Scanning System 

I decided to start the 3D scanning ball rolling by creating the SplineScan computer-controlled 
turntable. The turntable uses a gearbox for precise positioning, and has fixings for lasers, 
lights, and cameras. The obvious use of the turntable is for 3D scanning, although it can be 
adapted very easily to rotate objects for accurate photography or interactive display. 

I'm currently using the turntable to archive and measure ancient artifacts as part of my 
Ph.D. studies ( http://www.mara-3d.org ). and I have to say that I'm very happy with the 
results so far. 

The parts list might look a bit daunting, but the project is not difficult to make. The scanner 
itself consists of 3 main parts: 

Chassis This is the backbone of the scanner. Everything fits onto the chassis, and it needs 
to be rigid enough to withstand the weight of all the other components, and whatever you 
intend to put onto the turntable. 

Gearbox This part takes the turning force of the stepper motor and turns it into something 
more suitable for our needs. It's a simple design with only a few components. 

Electronics The brains and nerves of the scanner allow you control the turntable from your 
computer. The wiring is not difficult, and only limited soldering knowledge is required. 



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3D Scanning System 



Step 1 — Make the chassis. 





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3D Scanning System 

• Drill 4mm holes in the corners of the top and bottom plates, to accept the 65mm bolts that 
hold the chassis together. The 6 larger holes along the longest sides of the top plate are 
for the Vi" audio jacks. The outer diameter of the jack may vary depending on the brand 
you use. 

• Use the exploded parts diagram and the template to decide on the hole sizes for the other 
parts of the chassis. Hole sizes will vary depending on product brands, and the best rule 
(after "measure twice, cut once") is to start small and drill bigger if need be. 

• The small oblong marked on the top template is just a guideline for positioning the USB 
socket. The best source of USB sockets is a computer port extender that fits inside your 
computer and connects to the motherboard . Most computer shops have these on the 
shelf, but the design isn't standard and the mounting holes can be in any position. If you 
want to fit your USB socket to the chassis, now's a good time to mark and drill the holes 
using your socket as a template. 

• The 2 aluminum plates are held together by 75mm M4 bolts and spaced apart by bits of 
copper (or plastic) pipe. The exact diameter of the pipe is not important. Cut four 65mm 
lengths of pipe and put one at each corner of the top and bottom plates. Feed the bolts 
through the corner holes in the top and bottom plates, and secure them temporarily with a 
nut. Make sure everything lines up correctly, and then disassemble the parts again. 

• Now that all the holes are drilled, you can apply any finishing touches, like painting the 
copper and aluminum, and polishing any plastics. 

• The turntable is supported by 6 plastic ball casters, which can be pushed into place at this 
stage. These should be a tight fit, but a little glue won't do any harm. 

• Install the six Vi" jacks, which go down both sides of the top plate; these will let you use 2 
laser modules in various positions. With that done, you can turn your attention to the 
gearbox and motor. 



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3D Scanning System 



Step 2 — Make the gearbox. 






• Drill a hole through the center of the largest side of the box, to allow the shaft and the 
plastic worm drive to pass inside. Drill holes at the corners of the box that line up with the 
mounting holes on the motor, using the motor as a template. 

• Next, enlarge the hole in the plastic worm drive to 6.5mm so it will fit onto the motor shaft, 
and cut the worm drive to the length of the motor shaft. It should be a tight fit, and you 
might want to dab a little epoxy on the end to make sure the shaft stays put. 

• Drill 8mm holes through the narrowest sides of the box, to house the miniature shaft 
bearings. This step is quite tricky; the holes need to be positioned so that plastic cog and 
the worm gear mesh together accurately. Measure carefully, and allow plenty of tolerance 
in the motor mounting holes. Remember that it's much easier to reposition the motor than 
to reposition the bearings. 

• Push-fit the bearings into the holes (they shouldn't need glue) and then slide the shaft 
through the first bearing. This will be quite a tight fit, and might need a gentle tap with a 
heavy object to push the shaft through. 

• Now fit the motor (with the worm drive on the shaft) into position and bolt it in place. You 
can also move the 10-toothed gear on the 4mm shaft so that it meshes with the worm 
gear, and fix it into position using the small setscrew on its brass hub. 

• Fit the end caps in place, and you've almost completed the gearbox. Screw the gearbox 
into the chassis top with M3 screws, using the top as a template for the holes in the 
gearbox. If you use a 3.5mm drill bit, you can tap the holes in the gearbox and screw 
directly into it. You may want to include some packing washers between the top of the 
gearbox and the top plate of the chassis, to accommodate the plastic sides of the gearbox. 



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3D Scanning System 



Step 3 — Make the turntable. 




• Cut the turntable from a piece of 
3mm aluminum or rigid plastic 
using the template at 
splinescan.co.uk. Drill a 4mm hole 
in the center and fix a 4mm 
mounting hub in position, using a 
4mm shaft as a guide. You can 
glue this if you wish, but I modified 
the hub and used 3mm 
countersunk bolts to hold the hub in 
place. 

# Fit the turntable in position on the 
chassis, and cut the shaft so it 
won't protrude above the turntable. 
Fix the turntable onto the shaft by 
using a long Allen key to tighten the 
grub screw (setscrew) in the hub 
on the underside of the turntable. 
To finish the turntable, you can 
cover it in sticky-backed foam or 
paint it with a matte finish. 



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3D Scanning System 



Step 4 — Mount the electronics. 




• The Milford Instruments motor controller takes a serial port signal and converts it into 
motor movement. 

• The motor wires connect directly to the controller board, leaving only the power wires, 
which are attached to a 2.5mm DC socket on the side of the chassis. 

• I mounted the DC socket in an old blanking plate from the rear of a PC (the same plate I 
took the USB socket from). The DC socket is wired directly to the USB socket in the top of 
the chassis plate (red to red, black to black). Connection is made to the PC using an 
ordinary USB A-to-A cable. The motor controller needs 12V to operate, and 

• The power supply also powers the jacks. You can connect the jacks directly to power via 
the DC socket; this is acceptable if you don't like soldering and you want to keep things as 
simple as possible. 

• The drawback is that the power to the jacks will be constant, meaning that any laser 
emitters or lights plugged into the system will always be switched on, even when the 
machine is idle. 

• A more elegant solution is to draw power from the motor, using diodes to prevent current 
feeding back between the coils. The advantage of this method is that when the controller 
board powers down the motor, any lights or laser emitters will switch off. If the motor is 
idle but locked, the lights will be switched on. 

• NOTE: You can also use an Arduino with a suitable motor shield to control the 
stepper motor, and future versions of the scanner may use Arduino as standard. 
The truth is that I already have several of the Milford Instruments controllers left over from 
another project, and I don't have any spare Arduinos at the moment. 



O 



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3D Scanning System 



Step 5 — Make 2 laser emitters. 






• If you're interested in 3D scanning, then you'll need to make laser emitters to plug into the 
jacks. Similarly, you could make plug-in LED modules for illuminating objects on the 
turntable. 

• Power taken from the jacks will be around 12V, and since most laser emitters and LEDs 
use substantially less, you'll need to step down the power using a monolithic voltage 
regulator. I recommend the LM317, which can be wired to produce a range of different 
voltages. 

• The design of the emitter casings is quite simple. I used Neutrik cast phono plugs, which 
fit neatly into copper pipe. I had ample space to fit the power regulator circuit and a tiny 
laser line generator that I got on eBay. 

• I used a standard plumbing end-cap to finish the top of each emitter and then painted them 
black, and held the copper tube onto the cast plug using a combination of hot glue and grub 
screws. 



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3D Scanning System 



Step 6 — Install and run the control software. 




• Controlling the turntable is very 
easy using either Milford's own 
software or simple serial 
communication. I have provided a 
Python library to interface with 
these motor controllers, 
motorcon.py, in the code section of 
my website at 
http://www.monkeysailor.co.uk/code.php . 

• My "Babylon" version of the 
SplineScan software (I used it to 
scan Babylonian stone tablets) will 
support this turntable directly. It's 
completely open source and was 
released in December 2009 at 
splinescan.co.uk, so if you're 
interested in 3D scanning then 
you're in luck. SplineScan Babylon 
uses Python and Pygame, and has 
been designed to work on Linux, 
although it should work quite 
happily on Windows machines, too. 

• So, there you have it: an earnest 
attempt at a computer-controlled 
turntable suitable for open source 
3D scanning, photography, or 
display. I mounted mine in an outer 
casing, so I can scan objects 
without bouncing laser light all over 
the room. In the future, I might 
even modify the design to include a 
moving extrusion head, and 
develop a polar 3D printer. 



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3D Scanning System 



This project first appeared in MAKE Volume 21, page 54 
Related Posts on Make: Online: 

Handheld 3D Scanner 

http://blog. makezine.com/archive/2008/02. . . 
3D Scanning with a Web Cam and Projector 
http://blog. makezine.com/archive/2009/02. .. 

This document was last generated on 201 2-1 0-31 11 :06:1 7 AM. 



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